fix(dotfiles): make sure appended paths never spoil prepended paths
fix(dotfiles): make sure appended paths never spoil prepended paths

So when I wrote the parent commit I wondered why I was seeing the
Apple-provided `git --version` output instead of the one from the newer,
Homebrew-installed version.

Turns out that `/usr/local/bin` was getting prepended to the `$PATH`
(yay!) but later on when we appended `yarn global bin` (which is
`/usr/local/bin`, it would _move_ the directory to the end (boo!).

Fix is to do appends first, then prepends. That way prepending will
trump appending in the event that a $PATH appears in both lists.

Goodness knows how many times I've been using older Apple-provided stuff
instead of the newer Homebrew gear thanks to this bug... :facepalm: At
least since December 2020 it's been possible (75e38be9d0e08b6c2).

wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent,wincent/wincent